I found this video in amara.org This could be a helpful platform since some relevant projects are already there but also because they have made available a new interface where we can create or edit any idiom and timeshift it at the same time, split or merge strings according to the convenience of that language's grammar structure (sometimes some languages need more space than others). Also, it shows us how the subs will be showing on youtube as we do it, which is great, and if the project is connected to a YT channel, depending if the channel owner so decided, they will appear directly there. So, to proofread, improve or correct subs that are already public, is great! This is also a way to involve more people from the online translations phenomena.

The ideal is to do it in English first, with a good timing/strings structure and each language translation can use the English timings saving lots of effort. To translate and timeshift at the same time, even using the beta interface of amara which is really handy, is still a pain in the ass But it is worth the effort. How many people quit watching a video before finishing it without realizing that it is an uncomfortable reading that is making their brain not accept it so well?